Thanks for subscribing to Axios Science. Please consider telling your friends and colleagues to sign up. As always, you can send your feedback to me via andrew.freedman@axios.com, or just reply to this email.

As the U.S. heads toward a summer heat wave, we start off with something chilly, before heading to the tropics and on to the frontiers of AI. Have a great Fourth of July and see you on July 5.

1 big thing: The 'Atlantification' of the Arctic

A view of the Barents Sea near the settlement of Teriberka on the Arctic coast of northwest Russia. Photo: Lev Fedoseyev/TASS via Getty Images

The Arctic Ocean's boundaries are getting fuzzier as Atlantic waters push further northward and sea ice thins and melts more with each passing year, a new study finds.

Why it matters: If this trend continues, it could have wide-ranging impacts on lucrative fisheries, such as cod. It may already be altering weather patterns.

The basics: The Atlantic Ocean is well-mixed, with salty waters throughout the water column. In contrast, Arctic waters have clearly separated layers — on top there is freshwater, which can be cooled down in the fall to form sea ice, and then replenished in the spring and summer, when the sea ice melts.

The boundary between the Arctic Ocean and the Atlantic Ocean is defined by this physical difference, said the study's lead author Sigrid Lind of the Institute of Marine Research in Norway.

What they did: Researchers deployed sensors from ships to extend a long-running set of observations of the entire Barents Sea.

In total, the study relies on 76,000 profiles — made up of temperature and salinity measurements — of the water column in the Barents Sea, all taken in the late summer and early fall.

Of these, 18,000 profiles were from the central Barents Sea, and 7,000 were from the northern region.

They also used surface observations from Norway and Russia, as well as sea ice data from the National Snow and Ice Data Center in Colorado. The data used for the study spanned the period from 1970 through 2016.

What they found: The regional "hot spot" of warming is related to an oceanic invasion — the Atlantic Ocean is pushing farther north and east as the Arctic Ocean retreats.

The observations pointed to a more well-mixed, hotter and less ice-covered region just in the five-year stretch between 2011 and 2016, as compared to previous years.

The study found a sharp increase in the mixing and heat transport within the water column, and a decline in the freshwater present in the northern Barents Sea since 2010.

2. Earth lost a staggering amount of trees in 2017

Aerial view of deforestation in the Western Amazon region of Brazil on September 22, 2017. Photo: Carl De Souza/AFP/Getty Images

Last year saw the second-largest tropical tree cover loss on record since 1999, in large part because of human-caused fires in the Amazon, a new analysis from the World Resources Institute and University of Maryland found.

What it means: Trees absorb huge amounts of carbon dioxide, preventing even more global warming. Losing tree cover means there's the potential for accelerating warming, as well as a range of other effects, including damage to biodiversity, the loss of livelihoods for indigenous populations and greater susceptibility of the tropics to drought.

What they found: Using satellite data, the team found the tropics lost 15.8 million hectares, or 39 million acres, of tree cover in 2017. It's the equivalent of losing 40 footballs fields of trees a day for an entire year, researchers found.

Keep in mind: Tree cover loss is not the same as deforestation. Instead, it means the removal of tree canopy due to human and natural causes, and includes trees in plantations as well as natural forests.

Yes, but: The biggest contributor to forest cover loss is the clearing of forests for agriculture and other human uses.

Brazil was by far the greatest contributor to tree cover loss in tropical countries. There were 4.52 million hectares lost.

According to WRI and the University of Maryland report, the Amazon had more fires in 2017 than any other year since such monitoring began in 1999.

Tree cover loss in the Democratic Republic of Congo reached a record high in 2017, up by 6% over 2016.

3. AI takes on Hollywood's tedious tasks

An AI-generated graphical representation of a movie script. Image: Rivet.ai

A new company wants to help people make movies by outsourcing the grunt work — scheduling, budgeting, script analysis — to AI, Axios'Kaveh Waddell writes.

Starting from a human-written script, its algorithms can draft a budget and a shooting schedule, and even look for plot holes.

Why it matters: Debajyoti Ray, the founder of Rivet.ai, says that AI tools can cut down on uncertainty and allow production companies to take bigger risks.

Rivet.ai spun out of End Cue, the production company behind a trippy, nonsensical AI-written short film called Sunspring. Ray, whose background is in natural language processing, said his philosophy changed after Sunspring: His new company is focused mostly on analyzing human writing rather than trying to emulate it.

How it works:

In a few minutes, Rivet.ai's software can process a movie script and extract key elements from each scene: the characters involved, the location it takes place in, the props required, and the types of shots they call for. "This is a very laborious process" for humans, Ray said.

The software can then work out a shooting schedule that takes the availability of locations, props, cast and crew into account, plus weather forecasts.

Informed by the schedule, the platform can draw up a budget based on compensation, location and prop costs.

4. Axios stories worth your time

Meeting of the minds: Pope Francis is convening scientists, environmentalists and policymakers to try to spur action on climate change at a series of upcoming international summits, per Eric Lyman for Axios.

The quantum computing race: The U.S. and China are locked in a race to develop quantum technologies, which as Alison Snyder writes, "leverage fundamental properties of atoms and their subatomic particles to process and transmit information."

Delayed (again): Following an outside review, NASA is pushing back the launch date for the James Webb Space Telescope, this time to 2021. This is the latest in a series of delays and cost overruns.

5. Stories we're reading elsewhere

Artist impression of the interstellar comet ‘Oumuamua. Image: ESA

Asteroid: Japan’s Hayabusa2 probe made it to the asteroid that it will take three samples from over the next 18 months, per the AP’s Ken Moritsugu. “If the retrieval and the return journey are successful, the asteroid material could provide clues to the origin of the solar system and life on Earth,” he writes.

Climate: The unconfirmed 24-hour low temperature on Tuesday in Quiryat, Oman was 108.7 °F. If confirmed, this would be the warmest overnight low on record worldwide. Meanwhile, researchers observed ultra-low temperatures of about -144 °F in Antarctica, writes Tom Yulsman for Discover.

Bear cam is back: The Interior Department's most popular live cam, showing bears fishing for salmon at Katmai National Park in Alaska, is up and running.

6. Something wondrous

NASA released this image, showing estuaries near the coast of Guinea–Bissau in Africa, back on May 17. To me, this looks like a painting, complete with cerulean hues.

Here's NASA's explanation, posted at the agency's Earth Observatory website — a wormhole of a website for Earth science enthusiasts:

Estuaries near the coast of Guinea–Bissau branch out like a network of roots from a plant. With their long tendrils, the rivers meander through the country’s lowland plains to join the Atlantic Ocean. On the way, they carry water, nutrients, but also sediments out from the land.

The flat terrain in this small west African country is ideal for farming, particularly for rice cultivation, NASA writes. But land used for growing rice comes at the expense of protective mangroves, which form a buffer between the rivers and the lands. Erosion is now a problem along the Rio Geba, according to NASA, as is the issue of agricultural runoff into the water.